In joint replacement surgeries, sections of bones are removed and replaced by corresponding prosthesis. Typically, the surgeon selects a prosthesis size proportional to the bone size of the patient, and cuts the bone in order to match the size of the prosthesis, using cutting guides corresponding to the particular prosthesis being put in place. Validation blocks, which are typically prismatic, are inserted in the bone cut to validate that the bone has been cut to the proper size; if the block cannot be inserted, additional bone is cut until it can. Cement may also be used to compensate for poor cuts or uneven bones.